Right turn
Observing FR24 the latest ADSB transmission of the MAS370 is at 6.97N 103.63E at FL350. At this time the aircraft is over IGARI 6.94N 103.58E on the R208 at heading 25. Seems that MAS370 was cleared direct IGARI because slightly offtrack. IGARI is the last WPT before the FIR boundary WSJC Singapore / VVTS HoChiMinh. At 1720z, over IGARI, a right turn is initiated to BITOD to join the M765 as per FPL I presume.
The mag course between IGARI and BITOD is 059°. The last adsb transmission of the aircraft is 40 deg precisely during this right turn. Flight level remains unchanged but becomes 0ft as the turn is initiated.
Closest aircraft in the vicinaty of the MAS370 is the CES539 at FL360 6.03N 104.96E from PVG to KUL on the L642.